1. Field of the Invention
The present invention relates to improvement in cooling performance of a vehicle AC generator provided as a rotary electric machine on a vehicle or the like.
2. Description of the Background Art
As a conventional vehicle AC generator, Patent Document 1 (Utility Model Application Publication No. 5-2561) shows a vehicle AC generator having partition limbs with a clearance provided at its tip, the partition limbs radially extending from a bearing supporting portion of a front bracket, to partition an air inlet into multiple sections, and also preventing entry of relatively large foreign material from outside.
In such a configuration, even if a part of heat generated on a stator portion is transmitted to the front bracket through a stator iron core coupled by the front bracket and a rear bracket, only an arm portion is a path to the bearing supporting portion and therefore heat transmission to a bearing is reduced. In addition, the partition limbs extending from the bearing supporting portion function as radiating fins to release heat, thereby suppressing temperature increase in the bearing.
In addition, Patent Document 2 (Japanese Laid-Open Patent Publication No. 63-121455) shows a vehicle AC generator having partition limbs on an air inlet, formed by ribs provided on the outer circumference of a bearing retainer for bearing fixing.
This configuration makes it possible to, on the front attachment retainer for providing an effect of sizing up a fan and eventually improving the fan performance, form ribs that can prevent entry of foreign material at the air inlet and that are thinner than those provided for a die-cast front bracket, so as not to hinder ventilation.
The partition limb for heat release of Patent Document 1 is held at its one side by an aluminum-cast bracket. Therefore, if the axial length of the limb is extremely decreased or the thickness is decreased, a problem occurs with the strength of the limb as a part composing a product.
In addition, since the radial-direction length of the limb occupies almost the whole radial-direction width of the air inlet, the limb creates air flow resistance against the air inlet to no small extent. Thus, even though the limb may provide an effect of suppressing temperature increase in the bearing, the limb can deteriorate the cooling performance of the vehicle AC generator.
On the other hand, the retainer of Patent Document 2 mainly has a role to fix the bearing, and has a “foreign material entry preventing structure that does not reduce the air inlet area” as an accompanying structure. At any rate, an effect of aggressively reducing the temperature is not taken into consideration.